The long-term objective of this research is the development of a compact, robust, and user-friendly laser Source for 2-photon excitation in laser scanning microscopy. The use of 2-photon excitation in confocal microscopy offers a number of advantages for studies of cell physiology; however, the use of this technique is currently limited due to the specialized nature of the required sources of femtosecond duration pulses. 100- femtosecond pulses from a modelocked solid-state laser operating at wavelengths around 1.3 microns will be frequency-doubled to generate wavelength tunable ultrashort pulses in the desired wavelength range around 650 nanometers. A version of the modelocked laser which is pumped by an array of laser diodes will then be designed and built to reduce the size and enhance the stability and reliability of the source. There are no all-solid- state sources of 100-femtosecond pulses at the wavelengths which are needed, nor has there been a repone of a diode-pumped femtosecond laser at any wavelength. With a source having the required characteristics it will he possible to retrofit a large base of existing and future Scanning microscopes for 2-photon excitation.